---
title: "Road compaction specification, sand cone"
subject: "Soil Mechanics"
chapter: 5
key: "semester_4/soil_mechanics:road-compaction-sand-cone-check"
source: https://www.bctengineer.com/q/semester_4/soil_mechanics/road-compaction-sand-cone-check
site: BCT Engineering
---

# Road compaction specification, sand cone

Soil Mechanics · Chapter 5: Soil Compaction

- Asked in: 2075 Baisakh, 6 marks
- Video: [Chapter 6 Soil Compaction - Example 3 (Sand Cone Method)](https://www.youtube.com/watch?v=M8LFf6Lc5xw) — uSeeGeo
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_4/soil_mechanics/road-compaction-sand-cone-check
- Whole chapter: https://www.bctengineer.com/md/semester_4/soil_mechanics/chapter-5

## Question

In the construction of a road, the compaction specification required was 95% of Proctor maximum dry density at a field moisture content within 2% of the optimum moisture content. The maximum dry density and optimum moisture content obtained in the laboratory from the Standard Proctor test were 1.95 Mg/m³ and 13.5% respectively. A site engineer conducted sand cone test at two locations and obtained the following results.

| Location No. | Mass of soil removed (gm), Wet | Mass of soil removed (gm), Dry | Mass of sand used (gm) |
|---|---|---|---|
| 1 | 43.86 | 38.46 | 39.51 |
| 2 | 37.38 | 32.21 | 32.39 |

The density of sand used was 1.86 Mg/m³. Check whether the specification was satisfied or not.

## Short answer

Sand cone volumes are 21.24 and 17.41 cm3 for locations 1 and 2. Location 1 has RC 92.8% and w 14.0%, location 2 has RC 94.9% and w 16.05%; specification requires RC at least 95% and w 11.5-15.5%, so neither location satisfies.

## Answer

Sand cone test: volume of the hole = mass of sand filling it / density of sand. Then the field density and water content follow. The specification requires both

- $\gamma_d \ge 0.95\,\gamma_{d,max} = 0.95 \times 1.95 = 1.8525$ Mg/m³
- $w$ within $13.5 \pm 2\%$, that is 11.5% to 15.5%

#### Location 1

$$
V = \frac{39.51}{1.86} = 21.24\ \text{cm}^3
$$

$$
\gamma_{bulk} = \frac{43.86}{21.24} = 2.065\ \text{Mg/m}^3, \qquad \gamma_d = \frac{38.46}{21.24} = 1.811\ \text{Mg/m}^3
$$

$$
w = \frac{43.86 - 38.46}{38.46} \times 100 = 14.0\%
$$

$$
RC = \frac{1.811}{1.95} \times 100 = 92.8\%
$$

#### Location 2

$$
V = \frac{32.39}{1.86} = 17.41\ \text{cm}^3
$$

$$
\gamma_{bulk} = \frac{37.38}{17.41} = 2.147\ \text{Mg/m}^3, \qquad \gamma_d = \frac{32.21}{17.41} = 1.850\ \text{Mg/m}^3
$$

$$
w = \frac{37.38 - 32.21}{32.21} \times 100 = 16.05\%
$$

$$
RC = \frac{1.850}{1.95} \times 100 = 94.9\%
$$

#### Comparison

| Location | $\gamma_d$ (Mg/m³) | RC (%) | Required RC | w (%) | Allowed w |
|---|---|---|---|---|---|
| 1 | 1.811 | 92.8 | 95 | 14.0 | 11.5 to 15.5 |
| 2 | 1.850 | 94.9 | 95 | 16.05 | 11.5 to 15.5 |

**Answer: The specification is not satisfied. Location 1 fails on density (RC 92.8% < 95%) though its water content is acceptable. Location 2 is just below 95% (94.9%) and its water content (16.05%) is above the 15.5% limit. Both areas need re-rolling (and drying at location 2).**

The masses are taken as grams, as given; the result depends only on their ratios.

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. Sand cone hole volume:
   A. Sand/soil
   B. Mass of soil/density of sand
   C. Mass of sand / density of sand
   D. Wet soil/dry soil
   Answer: C. V = 39.51/1.86 = 21.24 cm3. (Key point: Hole volume)

2. Required dry density:
   A. 1.95
   B. 1.60
   C. 1.86
   D. 0.95 x 1.95 = 1.8525 Mg/m3
   Answer: D. RC 95% of MDD. (Key point: Requirement)

3. Location 1 fails because:
   A. w too low
   B. RC 92.8% < 95%
   C. Both fine
   D. w too high
   Answer: B. gd = 1.811 gives 92.8%. (Key point: Location 1)

4. Location 2 fails because:
   A. Only density
   B. RC 94.9% < 95% and w 16.05% > 15.5%
   C. Only water content
   D. It passes
   Answer: B. Both density and water content fail. (Key point: Location 2)

## Related in Soil Mechanics

- [Field compaction methods; Proctor curves](https://www.bctengineer.com/question.md?key=semester_4%2Fsoil_mechanics%3Afield-compaction-methods-proctor-curves) — Soil Mechanics, chapter 5
- [Compaction test: curve, MDD, OMC, RC](https://www.bctengineer.com/question.md?key=semester_4%2Fsoil_mechanics%3Acompaction-test-curve-mdd-omc-rc) — Soil Mechanics, chapter 5, asked 2×
- [Compaction test, RC and saturation](https://www.bctengineer.com/question.md?key=semester_4%2Fsoil_mechanics%3Acompaction-test-curve-saturation-degree) — Soil Mechanics, chapter 5, asked 2×
- [Embankment 95% compaction, 950 cc mould](https://www.bctengineer.com/question.md?key=semester_4%2Fsoil_mechanics%3Aembankment-95-compaction-950cc-mould) — Soil Mechanics, chapter 5
- [Cylindrical specimen, 95% compaction](https://www.bctengineer.com/question.md?key=semester_4%2Fsoil_mechanics%3Acylindrical-specimen-relative-compaction) — Soil Mechanics, chapter 5
- [Theoretical maximum dry density](https://www.bctengineer.com/question.md?key=semester_4%2Fsoil_mechanics%3Atheoretical-maximum-dry-density) — Soil Mechanics, chapter 5

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